Ammonia is one of the compounds released during the food spoilage process, so a device that can detect ammonia can be used as an indicator of food spoilage. This article reports on the preparation and characteristics of Starch/PVA composite films with Syzygium oleana as indicator films to detect ammonia vapor. The indicator was made by first preparing the starch / PVA composite films by casting method and then the films were dipped in Syzygium oleana extract. These films were characterized by using a UV-Vis spectrophotometer, Fourier Transformed Infra-Red Spectrophotometer and tested for mechanical properties such as tensile strength and elongation, and the water vapor transmission rate (WVT). The results showed that the addition of PVA reduced the absorbance value in the UV and visible area, the value of the water vapor transmission rate and the tensile strength but the elongation value of the film on the other hand rose. The indicator films can detect ammonia which was marked by its color change from red to blue. For further application, it can be used as a smart packaging label that can detect food freshness.